The present application is based on Japanese Priority Documents 2000-258763 filed on Aug. 29, 2000 and 2001-251943 filed on Aug. 22, 2001, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an inverter control circuit suitable for use in a motor-driven blower for an electric vacuum cleaner, a drive control circuit using the inverter control circuit, and an electric vacuum cleaner using the drive control circuit. The electric vacuum cleaner described herein includes various devices for collecting various solids or fluids into a collecting area by use of negative pressure.
2. Discussion of the Background
An electric vacuum cleaner needs to rotate a rotor of a motor used as a drive source therefor at high speed for the purpose of an improvement in dust""s suction performance. On the other hand, the conventional electric vacuum cleaner has a problem that since a commutator motor is used in its motor, the life of a brush becomes short with high-speed rotation of the commutator motor in the commutator motor accompanied by mechanical friction produced between a commutator and the brush, and sparks are produced from the brush according to conditions.
In order to overcome such a problem, such an electric vacuum cleaner using a brushless motor as described in Unexamined Patent Publication No. Sho 60(1985)-242827, or a method of controlling an electric vacuum cleaner using a brushless motor such as described in each of Examined Patent Publication Nos. Hei 7(1995)-28546 and Hei 7(1995)-28547 has been proposed.
There has recently been a demand for an electric vacuum cleaner intended for size and weight reduction and high performance in the field of the electric vacuum cleaner. Therefore, it becomes increasingly necessary to bring its motor portion into less size, increase its rotation velocity, bring its power consumption under control, and take countermeasures against noise produced from the electric vacuum cleaner, for example. Thus, the noise produced from the electric vacuum cleaner will be considered below.
Lots of sounds of types, which change in sound quality in proportion to a rotation velocity (rotational frequency) of a rotor of a motor, exist in characteristic sounds produced from the cleaner. They include, for example, a frequency sound identical to the rotational frequency, a frequency sound coincident with the product of the number of vanes or blades of an impeller and a rotational frequency, etc. A problem arises in that the frequency of a characteristic sound produced due to such a rotation velocity greatly changes when the cleaner is in use, i.e., while the cleaner is making cleaning. As a result, discomfort is given to a user. This is because since a suction port of the cleaner is placed on or separated from a cleaned surface, the state of the cleaned surface changes, and various types of dust are sucked into the suction port, a motor-driven blower placed under cleaning undergoes a sudden change in fluid load. Namely, since the rotation velocity (rotational frequency) of the rotor of the motor also changes suddenly with such a fluid load variation, the frequency of the characteristic sound produced due to the rotation velocity also changes, thus leading to discomfort being given to the user. In particular, uncomfortable feeling in the highest operation mode of the cleaner is great.
Accordingly, an object of the present invention is to reduce a change in characteristic sound produced due to a rotation velocity of a rotor of a motor, which gives uncomfortable feeling to a user.
The object of the present invention is achieved by the novel inverter control circuit suitable for use in a motor-driven blower for an electric vacuum cleaner, novel drive control circuit using the inverter control circuit, and novel electric vacuum cleaner using the drive control circuit of the present invention.
According to the novel inverter control circuit suitable for use in a motor-driven blower for an electric vacuum cleaner of the present invention, an inverter circuit, which has a plurality of switching elements and AC-drives the motor-driven blower according to periodic switching between these switching elements, are controlled based on detected value of physical quantity detecting means which detects physical quantities related to the electric vacuum cleaner. The inverter control circuit of the present invention includes means for setting a period in which a rotation velocity of the motor-driven blower is calculated, means for performing interrupt processing including a calculation of the rotation velocity of the motor-driven blower based on the detected value of the physical quantity detecting means, and means for generating a pulse signal according to a carrier wave having a period shorter than a period in which the rotation velocity of the motor-driven blower is calculated, and longer than the time required to perform interrupt processing including the calculation of the rotation velocity of the motor-drive blower, and inputting the pulse signal into a drive circuit which drives the switching elements of the inverter circuit according to the input pulse signal.
The present invention also defines the drive control circuit using the inverter control circuit and the electric vacuum cleaner using the drive control circuit.
According to the novel drive control circuit using the inverter control circuit, it is proved the inverter circuit which has a plurality of switching elements and AC-drives the motor-driven blower according to periodical switching between these switching elements, based on detected value of physical quantity detecting means which detects physical quantities related to the electric vacuum cleaner, and the drive circuit which drives the switching elements of the inverter circuit according to input pulse signal, as well as the above inverter control circuit.
According to the novel electric vacuum cleaner using the drive control circuit of the present invention, it is provided a housing having a fluid suction port, the motor-driven blower accommodated in the housing so as to be capable of sucking a fluid from the fluid suction port, and physical quantity detecting means which detects physical quantities related to the motor-driven blower, as well as the above drive control circuit.